In a number of metallurgical processes, it is often desirable to introduce reactive and nonreactive gases beneath the surface of molten metal contained in a refractory lined vessel. In the past, such gases have been introduced into the molten metal through a metal or ceramic tuyere or through a porous refractory element. Porous refractory elements have often resulted in nonuniform gas flow patterns and rapid wear of the porous refractory element, especially when used for introducing reactive gases. Metal or ceramic tuyeres, while providing a more uniform flow of gas, have also been subject to rapid wear and frequently plugging by solidified particles of the molten metal being treated. U.S. Pat. No. 4,535,975 discloses a metal encased refractory gas injection canister in which the gas is injected through a plurality of grooves cut in the refractory. The canister design of this patent is suitable only for low pressure gas injection since the sides of the can may bulge so that the refractory grooves cannot accurately contain high pressure gas flows. Furthermore, this prior design can only be used with gases which would not react with the refractory composition.